Based on advances in both our own work and also on confirming work of others, we are continuing to investigate the following areas: The origin of antibody diversity: Cloned hybridoma cell lines producing the lambda 1 light chain are being studied to determine the exact rules of amino acid replacement in complementarity-determining residues (CDR's). In addition, the ability of any particular vL to pair with the repertoire of vH's is being examined by a new technique involving the production and isoelectric focussing of vH fragments. This technique also has the potential to measure vH gene polymorphism.